Apparatus and process for separating particles



June 16, 1942. F. c. DYER HAL 2,286,607

APPARATUS AND PROCESS FOR SERARATING PARTICLES Filed March 6, 1939 IINVENTUHS Patented June 16, 1942 APPARATUS AND PROCESS FoR SEPARATINGPARTICLES Frederick Charles Dyer and Harold Langdon McClelland, Toronto,Ontario, Canada Application March 6, 1939, Serial ,No. 260,210 In CanadaMarch '7, 1938 11 Claims.

This invention relates to apparatus and process for separating particleshaving different characteristics, and is particularly adapted to theSeparation of seeds which because of their similarity of size, shape,weight, and/or specific gravity are not readily separable by knownmethods.

The present invention utilizes primarily a reciprocating or vibratingtable, which broadly is old in the art. In using the expression table,it is intended to include a travelling table, which may be in the formof an endless belt. Some of such tables stratify the particles by reasonof differences in specific gravity, and advance all the particles in onedirection by progressive motion, separation being obtained by reason ofthe fact that one class ortype of particle moves down the table morerapidly than the other, due to the movement and slope of the table andthe difference in specific gravity and size and also, in some cases,owing to differences in shape of the particles. In such tablesseparation is usually obtained by differences in the rolling or slidingcharacteristics of the particles. In most of such tables a comparativelylong stroke or reciprocating movement of one-quarter inch or more isused. In some cases air forced up through the table is used to keep themass of particles in a fluid condition.

While such tables are useful for separating certain particles, so far asis known, no such table ha ever made a substantially complete separationof particles of such similarity as to size, shape and weight as, forinstance, clover, alfalfa or alsike seeds from common weed seeds such asdodder, catchfiy, foxtail, or campion. To overcome this difiiculty thepresent apparatus and method was devised, although it is not limited toseparation of such closely similar particles, or the seeds referred toabove, but may be utilized in the separation of other particles, evensuch particles as might be separable by other known apparatus orprocesses.

Broadly speaking, the present invention consists in feeding theparticles to be separated to a table having asubstantially flat surface,substantially horizontal at least in its direction of reciprocatiomandcovered with fine, closely set, short resilient fibres normallysubstantially at right angles to said surface, and rapidly reciprocatingsaid table longitudinally in a direction Substantially parallel to theplane of its surface in a series of rapid forward and backward movementswith an interval of rest between each double movement in such a mannerthatin lieu thereof certain of said particles remain in the position atwhich they are fed to the surface, or move in one direction, and certainother particles having different characteristics move in the opposite ora different direction over the said surface. It will'appear from theabove that by this invention seeds having different characteristics maybe positively actuated in opposite or different directions, which actionis independent of any Sliding or rolling of the particles due to anyslope of the table, such as is obtained in prior constructions.

--A further feature of this invention resides in conditioning to createor accentuate a difference in the-surface characteristics of the seeds.This makes possible or improves the separation of such weed seeds asbuckhorn and pepper grass from clover.

The invention is hereinafter more particularly described and isillustrated'in the accompanying drawings in which Fig. l is adiagrammatic side elevation of one embodiment of the invention;

. Fig.'2 a plan view; r

Fig. 3 an end view of the reciprocating mech- A anism;

Fig.4 a graph representing the motion of a standard" table;

Fig. 5 a graph representing the ideal reciproeating movement of thetable; and

Fig. 6 a transverse sectional elevation of a modified form of table, ona reduced scale,

In the drawings corresponding numerals in the.

. or other means, although in a case Where a travelling surface isdesired for carrying away the separated Seeds, the fabric might be inthe form of a belt passing over and around the table from side to sideand reciprocable, transversely of its direction of travel, with thetable. It is also possible to construct a plurality of articulatedtables which travel in an endless chain in a direction at right anglesto the direction of the reciprocation or vibration thereof. In thespecification and claims, the word table is used broadly to include atable having a travelling surface, such as a belt passing thereover.

Strips 3 preferably extend over the surface of the table transverselythereof, dividing the surface into a plurality of panels.

The table I is mounted for longitudinal reciprocating movement. In theembodiment of our invention illustrated in the drawings resil ientsupports 4 are provided for supporting the table on a fixed base 5. Thesupports 4 may, as illustrated, consist of a plurality of strips ofresilient metal, such as thin steel secured to the base 5 and theunderside of the table 4 by means of screws. In order to prevent warpingor sagging, when the table is made of wood, and to ensure uniform.vibratory movement throughout the a table, a comparatively large numberof such supports may be provided, preferably uniformly spaced andlocated.

The table I is mounted substantially horizontally, although for specificpurposes, it is conceivable that for certain purposes the table might betilted slightly longitudinally at an angle to the horizontal, and for apurpose hereafter described it may be slightly tilted transversely.However, for the particular purpose for which the device was devised,namely the separation of certain weed seeds from crop seeds, it isessential that the table be as nearly horizontal as possible from oneend thereof to the other end. It is also important that the top of thetable be a substantially flat plane surface. Unevenness of the surfacewill introduce the element of gravitational flow which would interferewith proper separation under the influence of the vibratory movement. V

The vibratory movement may be obtained by any one of a number of means.It is necessary that the movement be in theplane of the surface of thetable. It must be rapid, and for the purpose of obtaining substantiallycomplete separation of the weed seeds and crop seeds specified above, itis essential that there be a brief interval of rest between eachvibratory cycle, comprising a forward and backward movement.

The vibratory movement may be obtained by striking one end of the tablewith light rapid sharp strokes of a hammer. Such a hammer might bemanually manipulated, but for practical purposes automatic mechanism isnecessary. The method illustrated has proved to be satisfactory andconsists of a weighted hammer head 6 mounted on a shaft 1. Provision ismade for varying the weight of the hammer by the addition of discs 8which may be secured in position by means of a lock nut 9, which alsolooks the hammer in position on the shaft I. The hammer head 6 may bescrewed on to the end of the shaft I, so that its position may bevaried.

The shaft 1 is adapted to reciprocate in bearings 22 and 23, and at theend thereof opposite fromthe hammer head is a tappet I0 whose positionis adjustable by means of the lock nuts II and I2. A spring I3 ismountedon the shaft I between the bearing 23 and a collar I4 on theshaft I, which spring tends to force the shaft I, and the hammer head 5against the end of the table I.

A cam I5 having an anti-friction striking roller I5, is mounted on arotating shaft I6, which may be driven by a motor or other suitablemeans. The cam I5 is so arranged relative to the tappet ID, that when itrotates it engages the said tappet I0 and forces the shaft 1 backward.When the cam disengages from the tappet ID, the spring I3 forces theshaft 1 forward and causes the hammer 6 to strike the end of the table,causing it to move forward sharply.

Secured to or engaging the other end of the table is a shaft I'Islidable in the bearing I8 and provided with a compression spring I9between the said bearing I8 and the collar 20 on the shaft. The forwardmovement of the table compresses the spring, which forces the tablesharply backward, the resilient supports I having sufiicient resilienceto permit the slight reciprocating movement, which is substantially lessthan onequarter inch in each direction. The resilient supports 4,however tend to regain a normal vertical position and to hold the tablein that position. When the table has been returned by the spring I9,there is a short period, before the cam I5 again engages the tappet I0,or at any rate before it disengages the tappet I0 so that there is aninterval of rest before the table is again struck by the hammer. Incommercial practice the movement ofthe hammer is, of course extremelyrapid, and the period of rest is not visible to the naked eye, but maybe traced on a graph. In Fig. 4 there has been represented the ordinarytype of vibration, which it will be observed is substantially continuousthere being practically no period of rest between the vibratorymovements. But, in Fig. 5, there is represented the ideal movement, inwhich there is a sharp quick forward movement followed immediately by asharp quick return movement, and with a sharp change of direction at thebeginning of each movement a short period between each double movementin which there is no movement at all. This, as explained, is the idealsituation, but in practice the period of rest is not so pronounced, asthere is inevitably a certain amount of induced vibration. However, itis believed that the nearer the movement approaches the ideal conditionillustrated, the better the separation. The natural tendency of theresilient supports 4 to return to the normal upright position tends toreduce the vibration, as does also the comparatively light pressure ofthe spring I3, which normally holds the hammer 6 against the end of thetable, until it is pulled back by the action of the cam. I5. However, tofurther dampen the induced vibration, a dampening spring 24 is mountedon the shaft II between the bearing I8 and an adjustable nut 2| on theshaft. It will be observed that when the shaft I! is moved by theforward movement of the table, the tension of the spring 24 is lessened,and when the shaft II moves in the opposite direction under the pressureof the spring I9, the spring 24 is compressed, and it is so adjustedthat it tends to prevent the table moving back beyond its normalposition, the tensioning, in fact, being such as to hold the shaft I1 ina predetermined normal position.

A rheostat or other suitable means is provided for regulating the speedof the motor driving the shaft I6, which in turn operates the cam I5,and therefore the speed of the action of the hammer may be regulated.Various other factors may be regulated by the adjusting means alreadydescribed. For instance the position of the tappet Ill may be adjusted,alsothe tension of the springs I3, I9 and 24, and the weight andposition of the hammer 6 may be varied. Inasmuch as there are so manyvariables, and the weight of the blow of the hammer, the length of theblow and its speed, also the length of travel of the table, all vary inaccordance with the circumstances, it is not possible to specify exactlyand definitely what these variable factors shall be. These factors alsodepend a great deal on the nature of the particles to be separated,including their weight, shape, and the nature of their surfaces. It isalso obvious, that some modification of the nature of the surface of thetable, or the stiffness of the spring mounting of the table might beeffective. The only way in which these variable factors may bedetermined in any particular case is by experiment, which, however, iswell within the capabilities of any person skilled in the art, whofollows the specification of the device herein set forth.

The device is operated as follows: The particles are fed in any suitablemanner, in its simplest form manually, but preferably by a dischargetrough of some kind to each panel of the separating table and inquantities sufficient that when the separating operation is complete theparticles will be spread over each panel not more than one particledeep, and preferably with a substantially clear space, which will becentrally of each panel. The particles will be fed to the panels usuallyabout along the centre line thereof, but since the number and speed ofmovement of the particles in one direction may be greater than in theopposite direction it may be preferable to feed the particles along aline closer to one side of the panel than the other.. The table isreciprocated, and the particles separate, the heavier particles movinglengthwise of the table in a direction opposite the direction ofmovement of the table initiated by each hammer blow, and the lighterparticles, having the same surface characteristics, travelling in thedirection of the initial movement. Similarly, with particles ofsubstantially the same weight, the smoother particles will move in adirection opposite to the direction of initial movement and rougherparticles will move in the direction of the initial movement. Separationmay also take place owing to differences in shape of the particles to beseparated. The strips which separate the panels limit the respectivemovements of the particles, so that when the separation operation iscompleted, the particles are arranged across the panels on oppositesides thereof adjacent the dividing strips, and may be removed in anyconvenient manner, such as by means of suction pipes along the edges ofthe panels. It is obvious that a continuous feed and continuous removalof the particles may be adopted.

As explained above, the frequency of reciprocation, the speed ofmovement, and other factors may be adjusted so that the maximumefficiency of separation is obtained. It is found, that other factorsbeing suitable, by increasing the speed of reciprocation and thefrequency, all of the particles, or substantially all of them, maytravel in one direction. By slowing down the speed of reciprocation andfrequency no movement, or a movement in the opposite direction mayresult. By simple experiment, the critical conditions under which theparticles to be separated travel in substantially opposite directionsmay be obtained.

In the case of separation of red clover, white clover, sweet clover,alfalfa or alsike from weed seeds such as dodder, catchfly or'campion,the slightly smoother, and sometimes heavier, crop seeds travel in adirection opposite to the initial hammer movement of the table, and theweed seeds travel in the direction of the initial movement of the table.

By tilting the table slightly transversely, as shown in Fig. 6, but notsuflicient to cause the seeds to roll or slide towards the side of thetable, unless the table is reciprocated, the seeds will not onlyseparate longitudinally of the table, but the separated seeds will tendto flow toward the lower edge of the table, and if suitable receptaclesare provided below the said lower edge of the table, the separated seedsmay continuously flow into such receptacles. This slight tilting, wouldalso improve the separation, since it would give fluidity to the mass ofparticles. A close observation of the table in operation indicates thatparticles moving in opposite directions during the separation processfrequently collide, and the separating process is thus slowed down. If,however, the particles are not only travelling in substantially oppositedirections lengthwise of the table, but are also moving slightly towardone side of the table, instead of the particles striking, so to speak,head on, they strike a glancing blow and may more readily pass oneanother. 'In this way the separation may be speeded up, but it should beclear that this effect is not analogous to methods of separation wherebydifferences in the capacity of the particles to slide or roll down anincline is utilized for separation. The movement across the table isprimarily to facilitate the discharge.

It will be clear from the above description that by the method proposedparticles of quite slight different characteristics may be separated.Larger particles'may be separated from smaller particles, heavierparticles from lighter particles, and smoother particles from rougherparticles.

Some seeds are so similar in all their characteristics that separationis difiicult or impossible in their natural state. Such seeds may besuccessfully separated by the process herein described by conditioningthem to create or accentuate a difference in a physical characteristicof some of the seeds relative to the others and in particular by takingadvantage of ac'haracteristic not heretofore mentioned. Some weed seedswhen moistened develop-a gelatinous outer coating, for example buckhornand pepper grass. Crop seeds, such as clover seeds, do not have thischaracteristic or have it in a much less degree. If, for example, seedscontaining buckhorn and pepper grass seeds are exposed to moisture whichmay beeither water or some other liquid either in the liquid state or inthe form of mist or steam and then mixed with or sprayed with a finelyground mineral or vegetable substance,

such as sawdust or ground quartz, the gelatinous coating developed bythe buckhorn and pepper grass causes the finely ground substance toadhere thereto so that the outer surface of the buckhorn and peppergrass seeds will become rough, whereas the surface of the clover seedswill remain smooth or will not pick up as much of the finely groundsubstance and therefore will not become as rough as the surface of theweed seeds. The treated seed when dried may be effectually separated bythe process and apparatus above described.

It should be noted that a process is in use at present which consists ofmoistening the seeds to be separated, the consequence of which is thatsome of the seeds acquire a gelatinous coating. By this process theseeds are then mixed with sawdust and, as a result of the sawdustadhering to one seed in preference to the other, separation may be hadby screening or specific gravity methods. This process fails when thegelatinous coating does not develop sufficiently during the time oftreatment to allow enough sawdust to adhere to effect the necessarydifference in physical characteristics. For instance, immature seedsdevelop a gelatinous coating more slowly than mature seeds with theresult that before screening or specific gravity separation it may benecessary to soak the seeds be yond the allowable wetting time in orderto create a sufficient gelatinous coating on the immature seeds, withthe result that the crop seeds may be spoiled. It should be understoodthat if treated for too long a time the moisture will penetrate theinside of the seed and spoil it. The allowable time varies according tothe seed treated and the manner in which it is treated, and theallowable wetting time can readily be determined by simple experiment.With the present process it is not necessary that the gelatinous coatingbe more than incipiently developed, because it is not necessary that anyconsiderable amount of the added dust-like substance shall adhere to theseed, but merely sufficient for the outer coat to become rough to agreater extent in the case of one seed than in the other. Thus acomparatively brief period of moistening is necessary. In screening orspecific gravity separation methods there must be sufficient sawdustadhering to the seeds to materially change the size or specific gravityI of those seeds which develop a gelatinous coating. It should be notedthat in the present process almost any dust-like substance may be used,but quartz dust or other finely ground mineral or metal substance ispreferred.

What we claim as our invention is:

1. Means for separating particles having different characteristics,comprising a table mounted for reciprocation, and having a substantiallyflat surface, substantially horizontal at least in its direction ofreciprocation and covered with fine, closely set, short, resilientfibres normally substantially at right angles to the surface to whichsurface the particles are fed; and means for rapidly reciprocating saidtable longitudinally in a direction substantially parallel to the planeof its surface to impart to the table a series of sharp quick forwardand backward movements with a sharp change of direction at the beginningof each movement and an interval of comparative rest between each doublemovement so that certain of said particles remain in the position atwhich they are fed to the surface or move in one direction and certainother particles having different characteristics move in the opposite ora different direction over the said surface.

2. Means for separating particles having differ ent characteristics,comprising a table mounted for reciprocation, and having a substantiallyfiat surface, substantially horizontal at least in its direction ofreciprocation and covered with fine, closely set, short, resilientfibres normally substantially at right angles to the surface to whichsurface the particles are fed; means for rapidly reciprocating saidtable longitudinally in a direction substantially parallel to the planeof its surface to impart to the table a series of sharp quick forwardand backward movements with a sharp change of direction at the beginningof each movement and an interval of comparative rest between each doublemovement so that certain of said particles remain in the position atwhich they are fed to the surface or more in one direction and certainother particleshaving different characteristics move in the opposite ora different direction overthe said surface; and means for dampeninginduced vibratory movements in the intervals of rest.

' 3. Means for separating particles having different characteristics,comprising a table mounted for reciprocation, and having a substantiallyflat surface, substantially horizontal in its direction of reciprocationand covered with fine, closely set, short, resilient fibres normallysubstantially at right angles to the surface to which surface theparticles are fed, and means for rapidly reciproeating said table withaseries of sharp quick forward and backward movements, with a sharpchange of directionat the beginning and end of each forward stroke, anda period of comparative rest before each forward stroke, the surface ofthe table being tilted transversely of the direction of itsreciprocating movement, sufficiently to impart a movement of theparticles across the table to discharge the separated particles at theside of the table, but not sufficient to impart a sliding or rollingmovement to the particles independent of the described movementinitiated by the reciprocation of the surface.

4'.' Means for separating particles having different characteristics,comprising a table mounted for reciprocation, and having a substantialflat surface formed by a short-pile fabric, substantially horizontal atleast in its direction of reciprocation; and means for rapidlyreciprocating said table with a series of sharp quick forward andbackward movements, with a sharp change of direction at the beginningand end of each forward stroke, and a period of comparative rest beforeeach forward stroke.

5. Means for separating particles having different characteristics,comprising a table having a substantially flat surface substantiallyhorizontal at least in its longitudinal direction and covered with fine,closely set, short resilient fibres normally substantially at rightangles to the surface, to which surface the particles may be fed;resilient supports for said table adapted to permit longitudinalreciprocation to and from its normal position; and'means for impartingto the table a series of sharp quick forward and backward movements witha sharp change of direction at the beginning of each movement and aninterval of comparative rest between each double movement.

6. Means for separating particles having different characteristics,comprising a table mounted for reciprocation, and having a substantiallyfiat surface, substantially horizontal at least in its direction ofreciprocation and covered with fine, closely set, short, resilientfibres normally substantially at right angles to the surface to whichsurface theparticles are fed; reciprocatin'g means for periodicallyforcing the table to move iii one direction with a sharp quick movement;and spring means adapted to return the table in the .opposite directionwith a sharp quick movement, whereby a rapid vibratory movement in adirection parallel to the plane of the surface of the table is impartedthereto, the stroke and frequency of the reciprocating means and thestrength of the spring means being relatively adjustable and adapted toprovide a desired length, speed and frequency of movement of the tableand to provide a sharp change of direction at the end of each forwardmovement and an interval of rest at the end of each return movement ofthe "table.

7. Means 'for'separating particles having difed for reciprocation, andhaving a substantially flat surface, substantially horizontal at leastin its direction of reciprocation and covered with fine, closely set,short, resilient fibres normally substantially at right angles to thesurface to which surface the particles are fed; reciprocating means forperiodically forcing the table to move in one direction with a sharpquick movement; spring means adapted to return the table in the oppositedirection with a sharp quick movement, whereby a rapid vibratorymovement in a direction parallel to the plane of the surface of thetable is imparted thereto, the stroke and fre quency of thereciprocating means and the strength of the spring means beingrelatively adjustable and adapted to provide a desired length, speed andfrequency of movement of the table and to provide a sharp change ofdirection at the end of each forward movement and an interval of rest atthe end of each return movement of the table; and a damper for dampeninginduced vibratory movements in the intervals of rest.

8. Means for separating particles having different characteristics,comprising a table having a substantially fiat surface substantiallyhorizontal in its direction of reciprocation and slightly tiltedtransversely thereof, and having its surface covered with a short-pilefabric; supporting means for said table adapted to permit a horizontalvibratory movement; means for imparting to the table a rapid series ofsharp quick movements in one direction; spring means for returning thetable in the opposite direction with a sharp quick movement, themovement imparting means being adjusted so that there is a sharp changeof direction at the end of each forward movement and a period of restafter the return movement of the table before imparting the next forwardmovement thereto; and means for dampening induced vibratory movements inthe period of rest.

9. Means for separating particles having different characteristics,comprising a substantially horizontal table mounted for longitudinalreciprocation in the plane of its upper surface; a surface covering forthe table of fabric having a short-pile of fine, closely set, resilientfibres; resilient means tending to maintain the table in a predeterminedinitial position; and positive means for imparting a series of sharpquick movements to the table in one direction from its initial position,a sharp quick return being effected by the resilient means aforesaid,and the said positive means being timed to allow a short period of restbetween each double movement of the table.

10. Process of separating particles having different characteristics ona table having a substantially fiat surface substantially horizontal atleast in its direction of reciprocation, and covered with fine, closelyset, short resilient fibres normally at substantially right angles tothe surface, comprising feeding the particles tothe table, and rapidlyreciprocating said table in a direction substantially parallel to theplane of its surface in a series of sharp quick forward and backwardmovements with a sharp change of direction at the end of each forwardmovement and a brief interval of rest between each double movementwhereby certain of said particles remain in the position at Which theyare fed to the surface or move in one direction and certain otherparticles having different characteristics move in the opposite or adifferent direction over the said surface.

11. Process of separating particles having different characteristics, asset forth in claim 10, in which induced vibratory movements in theintervals of rest are dampened.

his FREDERICK CHARLES DYER.

mark HAROLD L. MCCLELLAND. Witnesses to mark of Frederick Charles Dyer:

F. FRANK DYER, MRS. N. MAoKINNON.

